Artificial lowering of glacial lakes

Objective
Adaptation
Sectors
Water
Impacts addressed
Landslides
Water surges
Collection
Adaptation Technology Database
Technology group
Riverine flood protection
Technology reference
Commercial maturity
CTCN Keyword Matches
Disaster risk reduction
Nepal
Flow-through dam for flood control
Bhutan
Early Warning Systems Communication
Machinery
Community based
Storm surge barriers and closure dams
Multi-purpose dams

Adaptation Response

  • Reduces the occurrence or severity of floods and landslides in adjacent areas as well as downstream
  • Glacier lake outburt prevention

Description

Global warming is resulting in the world’s glaciers melting at a rapid rate, filling glacial lakes and increasing the likelihood of outburst floods (GLOFs). Floods and mudslides caused by GLOFs can have devastating impacts on communities lying below the lakes, posing a threat to both lives and infrastructure.The artificial lowering of glacial lakes is the process of draining water from those vulnerable to overflowing by digging a canal from the lake to a nearby river. Drainage reduces water level and decreases pressure on moraine dams. This in turn reduces the risk of burst events, which are increasingly likely as glaciers continue to melt. A glacial lake outburst flood (GLOF) is a type of outburst flood due to the increased volume of water in the lakes as a result of increasing temperatures. For e.g. GLOFs have led to devastating loss of life and infrastructure in the Himalayas. Artificial lowering of water levels of lakes is a technique to reduce the risk of glacial outburst.

Implementation

Implementation begins with a lake assessment to determine hazard potential that is usually carried out by a multidisciplinary team, including hydrological experts, geological experts and engineers. If a channel is warranted, the next step identifies a suitable excavation site. This may also include removal of the large boulders from the area. Rubble, loose rocks and turf are often used to build the channel walls.  Construction typically requires heavy machinery, though in some cases manual labour is used avoid further wall destabilization. Regardless of the intervention scale, the lake’s water level should be monitored continuously to minimize outburst flood risks. Early warning systems and disaster preparedness plans than include community awareness and trainings s can complement this work.

Cost

  • Costs for equipment, human resources, and maintenance
  • High costs (e.g. Thorthormi Lake project in Bhutan and Tsho Rolpa Lake project in Nepal range from $1 million to $3.2 million per lake (ADB, 2014)

Ease of Maintenance

Requires monitoring of lake levels and ongoing project inspection during and after implementation

Technology Performance

Lowering of lakes levels is most effective when combined with early-warning systems, preparedness training and planning

Environmental Benefits

- Reduces the risk of flooding and landslides, maintaining water storage capacity

Socioeconomic Benefits

- Protects people and infrastructure against the destructive (and expensive) effects of flooding and landslides.

- Avoids the need to undertake other risk management measures, such as the resettlement of nearby communities.

Opportunities and Barriers

Opportunities:

  • Implementing it in coordination with flood early warning systems and awareness raising campaigns for local communities improves its effectiveness
  • Reduces need for resettlement of populations near flood areas, and therefore reduces livelihood disruption
  • Increased storage capacity for water supply
  • High costs mean government cooperation is crucial and overseas financial assistance is often required

Barriers:

  • High cost technology
  • Heavy machinery may further destabilize moraine lake dams, therefore making it a complex and high risk intervention
  • Making changes to natural systems can have negative consequences elsewhere, for example. reducing water flow upstream can lead to shortages downstream
  • It is costly and complex due to the limited accessibility of many glacial lakes and lack of regular monitoring in remote areas

Implementation considerations*

  • Adapting natural systems such as this can have negative impact in other areas; for example, reducing the flow of water upstream may result in water shortage and drought downstream
  • Excavation activities can be dangerous for workers, and proper safety precautions must be ensured
  • Access to glacial lakes is often difficult and limited
  • The cultural significance of glacial lakes must be considered in any activity that seeks to change its natural structure specially in South Asia

Technological maturity:                3-5

Initial investment:                           2-5

Operational costs:                           2-3

Implementation timeframe:         3-4

 

* This adaptation technology brief includes a general assessment of four dimensions relating to implementation of the technology. It represents an indicative assessment scale of 1-5 as follows:

Technological maturity: 1 - in early stages of research and development, to 5 – fully mature and widely used

Initial investment: 1 – very low cost, to 5 – very high cost investment needed to implement technology

Operational costs: 1 – very low/no cost, to 5 – very high costs of operation and maintenance

Implementation timeframe: 1 – very quick to implement and reach desired capacity, to 5 – significant time investments needed to establish and/or reach full capacity

This assessment is to be used as an indication only and is to be seen as relative to the other technologies included in this guide. More specific costs and timelines are to be identified as relevant for the specific technology and geography.

Examples

Sources and further information